DESCRIPTION: This project seeks to understand how the responses to acoustic stimuli by inner hair cells (IHC) of the mammalian hearing organ are influenced by ionic currents passing through specific ion channels in the hair cell's basolateral membrane. A biophysical model predicts that among the effects of voltage-activated ion channels are likely to be a contribution to the adaptation of the hair cell to continuous sinusoidal stimulation and a hair cell equivalent of two-tone suppression. Whole-cell patch-clamp recording techniques will be carried out in intact cochleas removed from Mongolian gerbils and maintained by perfusion. Hair cell viability will be assessed using fluorescent dyes that indicate intracellular pH, membrane potential and synaptic vesicle recycling. Patch clamp data will be integrated into the biophysical hair cell model. Changes in membrane capacitance resulting from fusion of synaptic vesicles will be measured to characterize transmitter release. In addition to examining the basic biophysics of hair cell function, this work also contributes to the understanding of hair cell ionic homeostasis and thereby has relevance to understanding of hearing loss resulting from metabolic or other trauma to hair cells.